Lead-acid batteries use reactive sponge lead for the negative electrode, lead dioxide for the positive electrode, and dilute sulfuric acid for the electrolyte. During discharge of a lead-acid battery, the active material is electrochemically converted into lead sulfate by the acid, producing an electric charge. The amount of lead sulfate formed on the plates, and the amount of acid lost from the electrolyte are in exact proportion to the rate of discharge. The reverse action takes place when the battery is recharged.
Pure metal or alloy materials have little structural strength, and thus, require additional support for use. Attempts to reinforce such electro-chemical materials have been provided in various ways. Traditionally, metal materials, such as lead, have been alloyed with other materials to provide the necessary structural rigidity to the finished grid. This method is not optimal, as it requires manufacturing steps that may add to the overall cost. Moreover, alloy materials that have the required structural properties typically have poor electro-chemical properties and, thus, decrease the efficiency of the alloyed grid.
Lead grid materials have also been cast with other materials to provide the necessary structural rigidity to the finished plate. For instance, U.S. Pat. No. 4,456,666 describes such a casting process. Similar to the methods discussed above, casting requires costly manufacturing steps and tends to reduce the electro-chemical properties of the grid. Moreover, casting provides a material with increased structural rigidity in all directions, which presents a problem when forming expanded metal grids as described below.
The materials are then formed into expanded grids. U.S. Pat. Nos. 3,853,626 and 3,945,097 to Daniels et al. describe exemplary methods and equipment for making such expanded grids and are herein incorporated by reference in their entirety. Importantly, expanded grids are expanded along a single, longitudinal axis. Thus, processes such as casting, which provided mechanical strength in all directions are not compatible with such expansion methods and equipment. Production equipment for producing such expanded grids are available. Thus, it is desirable for composite materials to be formable into expanded grids using current production equipment.
Accordingly, there is a continuing need for non-alloyed materials having high structural properties that maintain the electro-chemical and mechanical properties of the preprocessed material. Additionally, there is a need for such non-alloyed materials that are formable into expanded grids using current production equipment.